caepentee: development of the oculomotoe neeve. 173 



lation with both the inferior branch of the third nerve and a communi- 

 cating ramus passing to it from the ophthalmic branch of the fifth. He 

 states that he found the origin of the ciliary ganglion difiScult to trace, 

 but is inclined to think that its cells come from the oplithalmic branch 

 of the trigeminus. At the origin of the commimicutiug branch from 

 the latter nerve, a small cluster of ganglion cells was found. 



Throughout the whole length of the third nerve, there could be seen, 

 disseminated among the nerve fibres, nuclei of cells, the interpretation 

 of which the writer found very difiicult. 



The ciliary ganglion was recognized by Dixon ('95) as a distinct cellu- 

 lar mass in a human embryo of the sixth week. It appears at first to 

 be more closely connected with the frontal and fourth nerves than with 

 the nasal and third nerves. It later shifts its position, and, by tlie 

 eighth week, has established connections as in the adult. (Comp. 

 Eeuter, '97.) 



Renter ('97), though concerned chiefly with the development of the 

 eye muscles in the pig, furnishes some interesting information in regard 

 to the early stages of the ciliary ganglion. He discovered, in an em- 

 bryo measuring 14 mm. from nape to rump, dift'erentiatiug ganglion 

 cells lying in the oculomotor nerve, both at the place where it divides 

 into its terminal branches and in the course of its long branch to the 

 ventral oblique muscle. In a later stage these cells are accumulated in 

 one mass in the form of a distinct ciliary ganglion. At the time of the 

 first appearance of the cells, no connection exists between the oculomo- 

 tor and the first branch of the trigeminus. Later, a radix longa is de- 

 veloped. The writer obtained no clew as to the source of the cells of 

 the ciliary ganglion, but, in view of the latter's late development, he 

 considers it very unlikely that its cells have any genetic connection with 

 the neural crest or the Gasserian ganglion. He is of the opinion that 

 His ('88") and Dixon ('95) have mistaken for the ciliary ganglion the 

 fundament of the dorsal oblique muscle during the period between 

 the disintegration of the neural crest and the first appearance of the 

 ganglion. 



It is evident from the foregoing reviews that, while observers agree 

 in the main as to the development of the abducent nerve, there is a 

 wide diversity of opinion in the cases of the oculomotor nerve and the 

 ciliary ganglion. Consequently, as far as the latter structures are con- 

 cerned, it is difficult to draw from the existing literature satisfactorily 

 supported generalizations. Especially is this true of the ciliary ganglion. 



